• When you clip an x-reference, you essentially trim part of the model space view in order to hide some of the model space objects while showing others. 
• This is a type of filter which allows you to select one or more x-references to clip while not selecting others. 
• It is useful to selectively show or hide different x-references at different locations. 
• If your drawing also has model space objects, then those also will not be affected by the x-clip polygon. 
• To change the dimensions of the x-clip polygon
  • Highlight the x-clip polygon
  • Grip one of the end points
  • Move the endpoint by drag and drop
  • And then repeat the x-clip command.

• The viewport is also a type of x-clip polygon, but it hides ALL model space objects outside of its boundary. 
• So if you are looking through a viewport and wish to hide all model space objects within a certain polygon,
  •  the easiest thing to do is to modify the viewport by drawing a new polygon and then use the _vpclip command. 
• When you want to change the dimensions of the viewport polygon itself
  • Click on the viewport polygon and drag a grip to the desired location. 
  • The window follows the viewport dimensions instantly.

WIPEOUT

• When you wish to use part of a source drawing as if it were x-clipped and yet you would also like to display part of that dwg without the rest of the background, use Wipeout
  • Create a closed polyline
  • Type Wipeout
  • Select P-line
  • Select OK
• Place the wipeout on a separate layer and freeze or thaw as needed in the Sheet dwg.
• An example can be found in S:/ACAD/10780/dwg/10780-C4-SS Plan West.dwg